The mastoid is named for the Greek word mastos (μαστός) meaning breast, and eidos meaning resemblance. This is reflective of the nipple-like shape of the mastoid process. It begins growing larger from birth but until puberty is is composed of cancellous or trabecular bone3 which is a type of bone that is less dense and softer than other bone, making it weaker and less stiff. After puberty the mastoid cells develop.

The mastoid process is also of clinical importance since the tissues in this region contain many interconnected air cells, called the mastoid cells, lined with mucus membranes which communicate with the middle ear. These air cells sometimes become infected when microbes from an infected middle ear spread to the mastoid region, via the aditus ad antrum and mastoid antrum, resulting in an infection called mastoiditis which can be of concern since this area is very close to the membranes that surround the brain and these membranes could also become infected. Complications of this condition include perisinuous abcess, periphleitis, and lateral sinus thrombosis.